<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <ol id="elem">
        <li>Hello</li>
        <li>World</li>
    </ol>

    <script>
        // 创建一个函数clear(elem) 用来移除元素里的内容。
        let elem = document.getElementById('elem');
        function clear(elem){
            elem.textContent = '';
        } 

        clear(elem); // 清除列表
    </script>
</body>

</html>